Restrict this transformation to equality conditions.
This transformation is not correct for not-equal conditions: (trunc x) != C1 & (and x, CA) != C2 -> (and x, CA|CMAX) != C1|C2 Let C1 == 0 C2 == 0 CA == 0xFF0000 CMAX == 0xFF and truncating to i8. The original truth table: x | A: trunc x != 0 | B: x & 0xFF0000 != 0 | A & B != 0 -------------------------------------------------------------- 0x00000 | 0 | 0 | 0 0x00001 | 1 | 0 | 0 0x10000 | 0 | 1 | 0 0x10001 | 1 | 1 | 1 The truth table of the replacement: x | x & 0xFF00FF != 0 ---------------------------- 0x00000 | 0 0x00001 | 1 0x10000 | 1 0x10001 | 1 So they are different. llvm-svn: 151691
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@ -753,7 +753,7 @@ Value *InstCombiner::FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS) {
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// (trunc x) == C1 & (and x, CA) == C2 -> (and x, CA|CMAX) == C1|C2
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// where CMAX is the all ones value for the truncated type,
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// iff the lower bits of C2 and CA are zero.
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if (LHSCC == RHSCC && ICmpInst::isEquality(LHSCC) &&
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if (LHSCC == ICmpInst::ICMP_EQ && LHSCC == RHSCC &&
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LHS->hasOneUse() && RHS->hasOneUse()) {
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Value *V;
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ConstantInt *AndCst, *SmallCst = 0, *BigCst = 0;
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